WTB: help fixing a humming F5 in MA

[sts9fan]

I have a 99% done F5 that hums in both channels. Is there anyone that would help fix it? I would be willing to pay and even ship the amp.
I am in eastern MA.

[KatieandDad]

Does it hum even with nothing connected to its inputs ?

Try disconnecting all leads to the inputs of the amp and see if that improves matters.

You need to ascertain wether this is supply or signal generated.

[sts9fan]

It hums without input.

[KatieandDad]

Try taking one amp in isolation and just connect supplies and the speaker.

The 0V from the amp MUST be connected to a single point close to the centre point of the two power supply capacitors.

0V or GROUND hum can often be caused if the 0V wire gauge is not heavy enough.

If you look at the multitude of photos of successful amps you will generally notice that the CENTRAL point between the power supply caps is a huge area of copper and that the 0V from the amp is connected to that mass of copper.

Also try disconnecting 0V from Mains Earth. LEAVE MAINS EARTH CONNECTED TO CHASSIS FOR SAFETY.

Have a look at these exampes.

[sts9fan]

I know this is not the correct location for this thread. I am looking for someone who is will to help in person or via shipping. I am tapped.
Here is what they would be dealing with.
https://picasaweb.google.com/lh/phot...eat=directlink

[KatieandDad]

Try connecting one amp as we have been discussing in PM.

Use HEAVY GAUGE wire for ALL 0V connections to the STAR point and isolate STAR 0V from Mains EARTH.

MAINS EARTH MUST still be connected to the chassis for safety.

[KatieandDad]

I can't impress enough the importance of the STAR 0V.

DO NOT connect 0V to mains Earth until the 0V is working correctly.

Make ABSOLUTELY SURE that the RCA input GND is NOT connected to the CHASSIS.

The 0V connections must also be VERY HEAVY cable.

Do not underestimate the problems that can occur with thin 0V leads.

[Pano]

Moved to Pass Labs

[mikojat]

Originally Posted by sts9fan

I have a 99% done F5 that hums in both channels. Is there anyone that would help fix it? I would be willing to pay and even ship the amp.
I am in eastern MA.

Hi Stefan, just take picture from top and place here...be sure, someone will help you..

[HIPCHECK]

I would really just start by taking everything back to building block stages. I would then dress the leads for each of those blocks. I would trim excess, twist the power leads, and lay out wiring paths that would be easy to follow.

This would clear up wiring so it can be better diagnosed. The current layout could be the problem.

Did you test it laid out before you mounted it in the chassis? I always build it in raw form and test with alligator clips, etc. If the unit worked then and now it is humming in the chassis that can be part of the problem.

Steve.